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Backwards Decoder??

I just installed a new Digitrax DH163AO into a new Genesis F3A with dual headlight housings with a small white and a small red light that are activated in Reverse in the upper housing and a single white light in the lower housing.

I replaced the factory decoder and connected each wire one at a time being careful not to reverse any of them (but it might have happened)

As soon as I applied power the main headlight lit up brightly, but briefly and has not lit up since. Also the controls were reversed with the loco running backwards in the Forward mode and visa versa. From previous experience I know that reversed controls and non working lights are the signs of a reversed decoder however I installed the new decoder in the same position as the factory original and according to the pictures in the Digitrax instructions.

Because this is not a plug-in decoder I couldn't simply turn it around. Instead I reversed the positive and negative leads. Now the loco runs in the proper direction but there are no lights whatsoever. I have not checked the bulbs yet but will probably do so tomorrow.

Anybody have any suggestions?

Thanks/Carter

Reply to
Carter Braxton
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I installed DH163A0s into three Genesis F units this weekend.

Did you install it with the component side up or down? If you installed it with the components facing up, everything will be reversed.

What size resistor did you use for the headlights? The Genesis series F units come with 1.5 Volt bulbs. If you don't add appropriate resistors, the bulbs will only last milliseconds before they burn out.

The DH163A0 is NOT like the DH163L0- it doesn't have any voltage or current-limiting circuitry to compensate for the low-voltage bulbs. All of its lighting outputs are 12-14 Volts. All that the "A0" designation means is that it's designed to physically fit into an Athearn Genesis locomotive.

If you only need the bulbs to turn on and off, a 1000 Ohm 1/2 Watt resistor works when connected in series between the function output and each bulb (one resistor per bulb). It won't allow for a good dimming effect if you want a Mars light or a Gyralight, however. That requires a couple of diodes in addition to each resistor as I described in the "Which decoder?" thread on the 8th.

-fm Webmaster, Rails on Wheels, Washtenaw County, Michigan's HO Modular Club, at

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Reply to
Fritz Milhaupt
  1. The F3 Genesis has its motor leads wired backwards, so you must reverse the leads. Sad but true.

  1. The A0 designation is for Atlas. It happens to fit in the Genesis.

  2. Resistors: in series with the single bulb: 680 ohms (HO power setting on Digitrax boosters).

  1. Resistors if you want two bulbs to light up at the same time: 560 ohms in series with both lights: all in series.

These resistor values are what I've used in the Santa Fe F7 with dual lower lights (wired in series, FOF, no mars), upper white light on F3 with Mars, upper red lights, FOR.

The best way to determine resistance is to get a bunch of resistors and starting with 1000 ohms, hook them up with the lights and progress to smaller value resistors until you get the brightness you want. I use a Loys Toys resistor tester to do that. It has a bunch of resistors inside and a rotary switch to select them. In combination with the Loys Toys decoders tester, it makes the whole thing pretty easy.

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Ed.

in article snipped-for-privacy@ferrousoxide.net, Fritz Milhaupt at snipped-for-privacy@ferrousoxide.net wrote on 1/21/04 4:03 AM:

Reply to
Edward A. Oates

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